In the following description, a disk is defined as a magnetic disk and a head is defined as a magnetic head.
This invention relates to a magnetic disk unit used in an electronic computer or as a storage device and more particularly to adjustment of the stop position of the magnetic head operatively linked with a driving stepping motor.
Recently, IC memories, magnetic tapes or magnetic disks are used as storage devices. However, IC memories are inconvenient in that they are volatile and the memory contents are lost when the electrical source is turned off inadvertently. Moreover, their storage capacity is rather low. Magnetic tapes are inconvenient for high speed data processing because of prolonged time involved in data retrieval. Thus a magnetic disk having a larger storage capacity and allowing for shorter accessing time has been desirable.
FIG. 1 shows an overall view of the conventional magnetic disk unit. A magnetic disk 1 has a number of concentrically arranged data tracks designed for data storage and can be rotated at a constant speed with the rotation of a spindle motor 2 for the reading or writing of data. A magnetic head 3 is positioned so that it is phasing both sides of the disk 1 at a small distance from the surfaces of the disk 1 and is moved along the disk surface to effect the reading or writing operations. The head 3 is moved by an actuator 5 driven by a stepping motor 4. The motors 2, 4 and the actuator are secured on a base 6. For correct data writing and reading into and from the magnetic disk 1, the magnetic head 3 needs to be stopped accurately on a selected one of the data tracks of the disk 1 without any positioning error.
In the conventional device, however, the stop position of the magnetic head 3 is governed by the stop angle of the stepping motor. The stepping motor is rotated stepwise although the step angle is small. However, even when the ambient temperature changes only slightly, the stop position of the magnetic head 3 on the selected track of the disk may deviate due to thermal expansions of the magnetic disk 1, actuator 5 and the base 6. This results in data reliability loss on account of the magnetic interference between the neighboring tracks. This presents problems when the number of tracks on the disk is to be increased.